Light Detection and Ranging (LIDAR) is an optical remote sensing technology that measures properties of scattered light to find range and other information of a distant target. Like the similar radar technology, which uses radio waves, the range to an object is determined by measuring the time delay between transmission of a light pulse (e.g., laser) and detection of the reflected light signal. The acronym “LADAR” (Laser Detection and Ranging) is often used in military contexts and may be interchangeable with the term “LIDAR.” The term “laser radar” may also be interchangeably used even though LIDAR does not employ microwaves or radio waves, which is definitional to radar.
LIDAR scanning may be employed to collect point samples on physical surfaces over large areas. In a LIDAR scanning process, a LIDAR scanning device transmits a laser signal across a scene that encompasses the target area of interest. The laser signal is reflected from the scene and captured by a detector in the LIDAR scanning device. As a result, the LIDAR scanning device measures a large number of points that lie on surfaces visible in the scene. Each scan point has a measured location in three-dimensional (3D) space (within some measurement error) that may be recorded relative to a point (x, y, z) in the local coordinate system of the LIDAR scanning device. The resulting collection of points is typically referred to as one or more point clouds. Each point cloud can include points that lie on many different surfaces in the scanned view.
A LIDAR apparatus employs a laser transmitter to transmit a pulse of light into the target area and a detector to measure the intensity scattered back from the target area. By measuring the scattering and attenuation experienced by the incident pulse of light, one can investigate the properties of the objects located in the target area. The light scattered back to the detector may result from interactions with objects within the target area located at various distances (i.e., ranges) with respect to the LIDAR apparatus. Because the light takes longer to return to the receiver from targets located farther away, the time delay of the return may be converted into a distance (range) between the objects and the LIDAR apparatus based on the speed of light. A conventional LIDAR apparatus may point the laser transmitter in various directions and at various angles with respect to the ground surface (i.e., scanning). A conventional LIDAR apparatus, however, may scan a target area in a point by point manner. That is, a detector may form an LIDAR image by scanning point by point along a row, similar to raster scan technology. Other conventional LIDAR apparatus may employ obtaining a volumetric assessment of a target area by obtaining multiple data sets from a variety of different directions. Such conventional methods may be relatively slow, expensive, and unreliable. Conventional methods may also be limited as to the number of spectral wavelengths that are detected at a single time. As a result, conventional methods may target a specific wavelength rather than obtaining a wide range of spectral data.